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Message-ID: <20180529100356.uimq6p6ihpx4eeur@lakrids.cambridge.arm.com>
Date: Tue, 29 May 2018 11:03:56 +0100
From: Mark Rutland <mark.rutland@....com>
To: YaoJun <yaojun8558363@...il.com>
Cc: kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org, jmorris@...ei.org
Subject: Re: [PATCH 0/4] migrate swapper_pg_dir
Hi,
On Tue, May 29, 2018 at 12:37:28PM +0800, YaoJun wrote:
> Because the offset between swapper_pg_dir and _text is fixed, when
> attackers break KASLR, they can calculate the address of swapper_pg_dir,
> and then they can apply KSMA(Kernel Space Mirror Attack). The principle
> of KSMA is to insert an entry to PGD, and this entry has type of block
> with AP = 01, so attackers can read/write kernel memory directly. Details
> can reference:
>
> https://www.blackhat.com/docs/asia-18/asia-18-WANG-KSMA-Breaking-Android-kernel-isolation-and-Rooting-with-ARM-MMU-features.pdf
>
> These patches migrate swapper_pg_dir to new place, and there is no
> relationship between swapper_pg_dir and _text. Because this is done
> during kernel booting, the physical address of new swapper_pg_dir may
> be fixed. Do we need to further randomize it?
This looks interesting, but this didn't go to all the relevant people.
Could you please resend this series, with at least the following Cc'd:
* linux-arm-kernel@...ts.infradead.org
* will.deacon@....com
* catalin.marinas@....com
Thanks,
Mark.
>
> YaoJun (4):
> Introduce a variable to record physical address of swapper_pg_dir.
> Introduce a variable to record new virtual address of swapper_pg_dir.
> Make tramp_pg_dir and swapper_pg_dir adjacent
> Migrate swapper_pg_dir and tramp_pg_dir.
>
> arch/arm64/include/asm/mmu_context.h | 6 +--
> arch/arm64/include/asm/pgtable.h | 2 +
> arch/arm64/kernel/cpufeature.c | 2 +-
> arch/arm64/kernel/entry.S | 4 +-
> arch/arm64/kernel/head.S | 10 ++--
> arch/arm64/kernel/hibernate.c | 2 +-
> arch/arm64/kernel/sleep.S | 2 +
> arch/arm64/kernel/vmlinux.lds.S | 10 ++--
> arch/arm64/mm/kasan_init.c | 6 +--
> arch/arm64/mm/mmu.c | 72 +++++++++++++++++++---------
> 10 files changed, 74 insertions(+), 42 deletions(-)
>
> --
> 2.17.0
>
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